Learning Forum

[Mr Eri MM]

Hello everyone,

 

I have a problem with flow between fixed parallel plates. On the top plate I have a no-slip condition. But on the bottom plate, I have a boundary condition where the velocity is non-zero. How can I add the boundary condition on the bottom plate? Would it be through a UDF? Looking through Fluent, I couldn't see an option in the wall tab.

[eric1234598765]

Hi,

What's the boudnary type of the bottom plate? If it is a interface, then choosing couple option in the mesh interface setting in Fluent could treat that boudnary as impermeable wall.

Otherwise, it is strange that Fluent can not set a no slip condition on a wall boudnary.

Eric

[Amine Ben Hadj Ali]

On the bottom wall: what do you know? Do you know the velocity of the wall? Does the fuild stick to that moving wall?

[Mr Eri MM]

Hello Eric and DrAmine.

In fact, it’s like the bottom plate has some holes where the fluid enters and leaves with a certain velocity defined by a boundary condition: (du/dy = alpha/ sqrt(k)) * (ui – um). That is, I need to set this condition exactly on the bottom wall.

Note that if this problem were to be solved analytically, I would have two boundary conditions.

(1) When y = 0 ==> du/dy = alpha/ sqrt(k)) * (ui – um)
(2) When y = h ==> u = 0

For the top plate the boundary condition it’s just a no-slip condition that can be set easily by fluent. But on the bottom plate I would need to put the equation: du/dy = alpha/ sqrt(k)) * (ui – um).

In short, what I really need to know how I can put an equation as a boundary condition on the bottom plate.

!Note that the plates are fixed.

 

[Amine Ben Hadj Ali]

Your BC looks after providing a shear stress to the Wall BC. You can explore that.

[Mr Eri MM]

Ok DrAmine, thank you.